1914.] HYDROUS CALCIUM VANADATES. 53 



or at least for the most part, during the later periods and upon heat- 

 ing. If present in some quantity it reveals itself by a white crystal- 

 line deposit in front of the boat. 



The contents of the receptacles and of the tube were finally evapo- 

 rated in porcelain with sulphuric acid, which was then heated till 

 fumes arose. After dilution, the deep blue solution was transferred 

 to a flask, saturated with hydrogen sulphide gas, and heated while 

 the gas still passed. The flask was then stoppered and allowed to 

 stand, over night as a rule, before filtering. The molybdenum sul- 

 phide was roasted to oxide. 



The filtrate was brought to boiling in a flask while passing carbon- 

 dioxide gas until hydrogen sulphide was wholly expelled, then titrated 

 in the flask at 70°-8o° with permanganate. The vanadium was 

 again reduced, this time with sulphur-dioxide gas, which in turn was 

 expelled by boiling in a current of carbon dioxide, and the vanadium 

 was again titrated. If desired tlje operations of reduction and titra- 

 tion were repeated. The values obtained after successive repetitions 

 of the reduction by sulphur dioxide agreed well but were always 

 somewhat lower than after reduction by hydrogen sulphide. The 

 difiference is no doubt due to the presence in the one case of a little 

 free sulphur from the hydrogen sulphide, which consumes perman- 

 ganate at the high temperature of titration. If the molybdenum sul- 

 phide has been filtered through paper instead of a Gooch crucible, 

 permanganate is also consumed by organic extracts from the paper. 



Summary. 



Two apparently different calcium vanadates are described, which 

 resemble each other very closely and have the same composition — 

 CaO-3V„05-9H20 — ^when holding their maximum water content at 

 roon> temperatures. One of them — hewettite — occurs at Minas- 

 ragra, Peru, and has been noticed on a single specimen from Para- 

 dox Valley, Colorado. The other — metahewettite — occurs at nu- 

 merous localities in western Colorado and eastern Utah. Both min- 

 erals are sparingly soluble in water. 



A third calcium vanadate — pascoite (2CaO-3V205- ii ?HoO) — 

 is also described. This occurs with hewettite at Minasragra. It is 

 very soluble in water. 



